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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="math_toolkit.pol_overview"></a><a class="link" href="pol_overview.html" title="Policy Overview">Policy Overview</a>
</h2></div></div></div>
<p>
      Policies are a powerful fine-grain mechanism that allow you to customise the
      behaviour of this library according to your needs. There is more information
      available in the <a class="link" href="pol_tutorial.html" title="Policy Tutorial">policy tutorial</a>
      and the <a class="link" href="pol_ref.html" title="Policy Reference">policy reference</a>.
    </p>
<p>
      Generally speaking, unless you find that the <a class="link" href="pol_tutorial/policy_tut_defaults.html" title="Policies Have Sensible Defaults">default
      policy behaviour</a> when encountering 'bad' argument values does not meet
      your needs, you should not need to worry about policies.
    </p>
<p>
      Policies are a compile-time mechanism that allow you to change error-handling
      or calculation precision either program wide, or at the call site.
    </p>
<p>
      Although the policy mechanism itself is rather complicated, in practice it
      is easy to use, and very flexible.
    </p>
<p>
      Using policies you can control:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">How results
          from 'bad' arguments are handled</a>, including those that cannot be
          fully evaluated.
        </li>
<li class="listitem">
          How <a class="link" href="pol_ref/internal_promotion.html" title="Internal Floating-point Promotion Policies">accuracy is
          controlled by internal promotion</a> to use more precise types.
        </li>
<li class="listitem">
          What working <a class="link" href="pol_ref/precision_pol.html" title="Precision Policies">precision</a>
          should be used to calculate results.
        </li>
<li class="listitem">
          What to do when a <a class="link" href="pol_ref/assert_undefined.html" title="Mathematically Undefined Function Policies">mathematically
          undefined function</a> is used: Should this raise a run-time or compile-time
          error?
        </li>
<li class="listitem">
          Whether <a class="link" href="pol_ref/discrete_quant_ref.html" title="Discrete Quantile Policies">discrete
          functions</a>, like the binomial, should return real or only integral
          values, and how they are rounded.
        </li>
<li class="listitem">
          How many iterations a special function is permitted to perform in a series
          evaluation or root finding algorithm before it gives up and raises an
          <a class="link" href="error_handling.html#math_toolkit.error_handling.evaluation_error">evaluation_error</a>.
        </li>
</ul></div>
<p>
      You can control policies:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          Using <a class="link" href="pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">macros</a>
          to change any default policy: the is the preferred method for installation
          wide policies.
        </li>
<li class="listitem">
          At your chosen <a class="link" href="pol_ref/namespace_pol.html" title="Setting Polices at Namespace Scope">namespace
          scope</a> for distributions and/or functions: this is the preferred
          method for project, namespace, or translation unit scope policies.
        </li>
<li class="listitem">
          In an ad-hoc manner <a class="link" href="pol_tutorial/ad_hoc_sf_policies.html" title="Changing the Policy on an Ad Hoc Basis for the Special Functions">by
          passing a specific policy to a special function</a>, or to a <a class="link" href="pol_tutorial/ad_hoc_dist_policies.html" title="Setting Policies for Distributions on an Ad Hoc Basis">statistical
          distribution</a>.
        </li>
</ul></div>
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<div class="copyright-footer">Copyright © 2006-2021 Nikhar Agrawal, Anton Bikineev, Matthew Borland,
      Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert Holin, Bruno
      Lalande, John Maddock, Evan Miller, Jeremy Murphy, Matthew Pulver, Johan Råde,
      Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, Thijs van den Berg, Daryle
      Walker and Xiaogang Zhang<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
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